This invention relates to a medical instrument comprising a connector of a rigid resin difficult to bond with a curable adhesive and a tube of a flexible resin bondable with such a curable adhesive wherein the connector and the tube are joined to form a continuous passage for transferring liquid through the instrument.
In general, most medical instruments for transferring liquid therethrough include a plurality of parts of different materials which are bonded one another. One such example is a winged venous infusion needle assembly. A needle is secured in a connector of rigid polypropylene resin which is, in turn, bonded or connected to a tube of flexible polyvinyl chloride resin with an adhesive of solvent type using, for example, tetrahydrofuran (THF) and methyl ethyl ketone (MEK).
Materials difficult to bond with adhesive, for example, polypropylene must be subject to a plasma treatment for sealing. Such plasma treatment is carried out by exciting oxygen gas or laughing gas in vacuum by high frequency discharge, applying the thus created plasma to a surface of the difficult-to-bond material to form active radicals such as carboxyl and carbonyl radicals on the surface. The thus activated surface enables adhesive bonding.
The use of solvent-type adhesive, however, gives rise to a number of problems. (1) Solvent attacks parts to be bonded which become brittle or weak and will eventually be broken. (2) Some material is dissolved from parts by solvent and will undesirably block a flowpath. (3) Residual solvent leaves the risk of toxicity. Medical instruments having parts bonded with such solvent-type adhesive suffer from these and other problems. There is the need for a technique capable of bonding parts without using an organic solvent.
Japanese Patent Application No. 58-199699 filed on Oct. 25, 1983 in the name of Terumo Kabushiki Kaisha proposed a medical instrument for transferring liquid therethrough, comprising a connector of a rigid resin including a generally cylindrical portion having a passage extending throughout the connector and one open end, the cylindrical portion at the one open end including an outer sleeve and an inner sleeve defining therebetween a recess extending circumferentially and axially from the open end, the inside surface of the outer sleeve being provided with at least one substantially circumferential rib; and a tube of a flexible resin inserted into the recess and bonded thereto with an adhesive to define a continuous passage communicating the connector and the tube. The present invention is a further improvement in a medical instrument of this type.